Formal System Model Research Articles

Formal modeling and verification of fractional order linear systems

This paper presents a formalization of a fractional order linear system in a higher-order logic (HOL) theorem proving system. Based on the formalization of the Grünwald–Letnikov (GL) definition, we formally specify and verify the linear and superposition properties of fractional order systems. The proof provides a rigor and solid underpinnings for verifying concrete fractional order linear control systems. Our implementation in HOL demonstrates the effectiveness of our approach in practical applications.

Modeling and simulation of a controlled steam generator in the context of dynamic reliability using a Stochastic Hybrid Automaton

The paper proposes a modeling framework to support Monte Carlo simulations of the behavior of a complex industrial system. The aim is to analyze the system dependability in the presence of random events, described by any type of probability distributions. Continuous dynamic evolutions of physical parameters are taken into account by a system of differential equations. Dynamic reliability is chosen as theoretical framework. Based on finite state automata theory, the formal model is built by parallel composition of elementary sub-models using a bottom-up approach. Considerations of a stochastic nature lead to a model called the Stochastic Hybrid Automaton. The Scilab/Scicos open source environment is used for implementation. The case study is carried out on an example of a steam generator of a nuclear power plant. The behavior of the system is studied by exploring its trajectories. Possible system trajectories are analyzed both empirically, using the results of Monte Carlo simulations, and analytically, using the formal system model. The obtained results are show to be relevant. The Stochastic Hybrid Automaton appears to be a suitable tool to address the dynamic reliability problem and to model real systems of high complexity; the bottom-up design provides precision and coherency of the system model.

MAPE-K Interfaces for Formal Modeling of Real-Time Self-Adaptive Multi-Agent Systems

Formal modeling of multi-agent systems is an active area of research. The use of precise and unambiguous notation of formal methods is used to accurately describe and reason about the system under consideration at the design time. Multi-agent systems deployed in dynamic and unpredictable environment needs to have the ability of self-adaptation, making them adaptable to the failures. State of the art encourages the use of MAPE-K feedback loop for the provision of self-adaptation in any system. There is a dire need of formal vocabulary that can be used for the conceptual design of any real-time multi-agent system with self-adaptation. In this paper, we have proposed a set of predefined interfaces for the provision of self-adaptation in real-time multi-agent systems. The interfaces are based on monitor, analyze, plan, and execute phases of the MAPE-K feedback loop. We formally specify our interfaces using timed-communicating object-Z language. The complete framework is elaborated using a trivial case-study of conveyor belt system based on a real-time agent architecture.

Modeling and Control of an Automated System in Surgical Microscopy Based on Petri Nets

This scientific study makes reference to the modeling, control, and failure diagnosis based on Petri-Net based machine (PN) system. The described system incorporates an automated ophthalmic surgical microscope which is utilized here. The approach for its design and function concerns control logic based applications, particularly, extended Hierarchical Petri Nets GHENeSys and language programming for the coordination of timed continuous activities and the use of CCS compiler. Due to the fact that the control system is based on discrete events, a formal PN system model was adopted. The aim to verify the feasibility of the functional properties and structure of the model is proposed in order to achieve greater efficiency in the control design as well as considering a failure-tolerant control system.

A Denotational Mathematical Theory of System Science: System Algebra for Formal System Modeling and Manipulations

A Denotational Mathematical Theory of System Science: System Algebra for Formal System Modeling and Manipulations

계층적 실시간 시스템 스케줄링 검증을 위한 정형적 프레임워크

The use of Operating System(OS) virtualization is increasing as it provides many useful features such as efficient use of hardware(HW), easy system migration, and isolation between virtual spaces which prevents errors effecting each other. Recent development in HW has made it possible to use OS virtualization in embedded systems. However, implementing OS virtualization means that a multiple number of schedulers are layered in a system, rendering it difficult to analyze the schedulability of the system and errors are easily produced. Errors in safety critical embedded systems can cause serious damage to life and property; thus, the hierarchical schedulability must be verified. In this paper, we propose a framework which supports formal modeling and verification of hierarchical scheduling systems with UPPAAL.

Identity-Based Distributed Provable Data Possession in Multicloud Storage

Remote data integrity checking is of crucial importance in cloud storage. It can make the clients verify whether their outsourced data is kept intact without downloading the whole data. In some application scenarios, the clients have to store their data on multicloud servers. At the same time, the integrity checking protocol must be efficient in order to save the verifier's cost. From the two points, we propose a novel remote data integrity checking model: ID-DPDP (identity-based distributed provable data possession) in multicloud storage. The formal system model and security model are given. Based on the bilinear pairings, a concrete ID-DPDP protocol is designed. The proposed ID-DPDP protocol is provably secure under the hardness assumption of the standard CDH (computational Diffie-Hellman) problem. In addition to the structural advantage of elimination of certificate management, our ID-DPDP protocol is also efficient and flexible. Based on the client's authorization, the proposed ID-DPDP protocol can realize private verification, delegated verification, and public verification.

Modeling and Verification of Reconfigurable and Energy-Efficient Manufacturing Systems

This paper deals with the formal modeling and verification of reconfigurable and energy-efficient manufacturing systems (REMSs) that are considered as reconfigurable discrete event control systems. A REMS not only allows global reconfigurations for switching the system from one configuration to another, but also allows local reconfigurations on components for saving energy when the system is in a particular configuration. In addition, the unreconfigured components of such a system should continue running during any reconfiguration. As a result, during a system reconfiguration, the system may have several possible paths and may fail to meet control requirements if concurrent reconfiguration events and normal events are not controlled. To guarantee the safety and correctness of such complex systems, formal verification is of great importance during a system design stage. This paper extends the formalism reconfigurable timed net condition/event systems (R-TNCESs) in order to model all possible dynamic behavior in such systems. After that, the designed system based on extended R-TNCESs is verified with the help of a software tool SESA for functional, temporal, and energy-efficient properties. This paper is illustrated by an automatic assembly system.

Real-Time Languages, Timed Alternating Automata, and Timed Temporal Logics: Relationships and Specifications

Abstract Time dependent models have become increasingly important in formal modeling and verification of software systems. In this paper, we investigate the expressiveness of real-time iterative arrays and trees in the context of language recognition. Such synchronous parallel models of computation must meet high dependability requirements in performing complex interactions in a real-time envi- ronment. Furthermore, we present timed event alternating automata which do not only describe a theoretical model framework for formal languages but establishes strong relationships and foundations to timed propositional temporal logic through two embedded powerful metaphors – alternation and time.

Системное моделирование международных отношений

The article provides an overview of international and Russian literature on the genesis and development of System Research in IR studies, demonstrates the emergence of System Research in Russia and in the world, the development of the general theory of systems. It is shown that at the first stage, the representatives of natural sciences tried to identify the isomorphism between the international relations system and other systems (biological, physical). In this context, the attempts to form a general theory of international conflict could be viewed. It is noted that at the beginning of the 1970s, these attempts ended unsuccessfully in general. The second area of international relations system modeling is related to the work of structural realists, primarily K. Waltz and M. Kaplan. Despite the fact that in their papers the verbal analysis dominates over the formal international relations system model, they have made a significant contribution to the political science in perception of the systems theory. The paper also describes the system modeling in the context of the Neo-Marxist theory of international relations, first and foremost, in the meaning of the I. Wallerstein's world-system theory. Special attention is paid to the systemic research crisis in the IR science at the turn of 1980–1990s, also due to a sharp change in the international situation, and the transition from a predominantly deterministic world of the Cold War to the post-bipolar non-equilibrium international system. The authors clearly reveal the evolution of the international relations perception in terms of the systems theory. They also illustrate the intensification of the international system modeling in the XXIst century on the basis of a new methodology – via the use of the more sophisticated complexity theory (the theory of complex systems), as well as by adapting the sociological theory of structuration by A. Giddens in political sciences. Showing the most promising areas of the complexity theory practical application in the modeling of international relations – agent-based modeling and simulation of system dynamics, – the authors enumerate the most promising spheres for the system modeling in international studies.

Formal Modeling and Verification of Context-Aware Systems using Event-B

Context awareness is a computing paradigm that makes applications responsive and adaptive with their environment. Formal modeling and verification of context-aware systems are challenging issues in the development as they are complex and uncertain. In this paper, we propose an approach to use a fo

Building high assurance human-centric decision systems

Many future decision support systems will be human-centric, i.e., require substantial human oversight and control. Because these systems often provide critical services, high assurance is needed that they satisfy their requirements. This paper, the product of an interdisciplinary research team of experts in formal methods, adaptive agents, and cognitive science, addresses this problem by proposing a new process for developing high assurance human-centric decision systems. This process uses AI (artificial intelligence) methods--i.e., a cognitive model to predict human behavior and an adaptive agent to assist the human--to improve system performance, and software engineering methods--i.e., formal modeling and analysis--to obtain high assurance that the system behaves as intended. The paper describes a new method for synthesizing a formal system model from Event Sequence Charts, a variant of Message Sequence Charts, and a Mode Diagram, a specification of system modes and mode transitions. It also presents results of a new pilot study investigating the optimal level of agent assistance for different users in which the agent design was evaluated using synthesized user models. Finally, it reviews a cognitive model for predicting human overload in complex human-centric systems. To illustrate the development process and our new techniques, we describe a human-centric decision system for controlling unmanned vehicles.

Automatically Generating Specification Properties From Task Models for the Formal Verification of Human–Automation Interaction

Human-automation interaction (HAI) is often a con- tributor to failures in complex systems. This is frequently due to system interactions that were not anticipated by designers and an- alysts. Model checking is a method of formal verification analysis that automatically proves whether or not a formal system model adheres to desirable specification properties. Task analytic mod- els can be included in formal system models to allow HAI to be evaluated with model checking. However, previous work in this area has required analysts to manually formulate the properties to check. Such a practice can be prone to analyst error and oversight which can result in unexpected dangerous HAI conditions not be- ing discovered. To address this, this paper presents a method for automatically generating specification properties from task models that enables analysts to use formal verification to check for system HAI problems they may not have anticipated. This paper describes the design and implementation of the method. An example (a pilot performing a before landing checklist) is presented to illustrate its utility. Limitations of this approach and future research directions are discussed.

System Design Model for Versatile Outbreak Surveillance

Unlike usual surveillance systems, the ASTER system must provide a unified monitoring of several military populations exposed to different biological and chemical threats, and the surveillance of each population must be tailored to meet its specific risk profile. For coping with these requirements, we have developed a formal surveillance system model we have used for designing the system architecture and the webservices collaborations. The system currently covers populations in desertic areas as well as in Amazonian Forest. This versatility allowed a quick and easy system tailoring for the recent French Deployments in Jordanian Refugees Camps or in Mali.

Generating Erroneous Human Behavior From Strategic Knowledge in Task Models and Evaluating Its Impact on System Safety With Model Checking

Human-automation interaction, including erroneous human behavior, is a factor in the failure of complex, safety-critical systems. This paper presents a method for automatically generating formal task analytic models encompassing both erroneous and normative human behavior from normative task models, where the misapplication of strategic knowledge is used to generate erroneous behavior. Resulting models can be automatically incorporated into larger formal system models so that safety properties can be formally verified with a model checker. This allows analysts to prove that a human-automation interactive system (as represented by the formal model) will or will not satisfy safety properties with both normative and generated erroneous human behavior. Benchmarks are reported that illustrate how this method scales. The method is then illustrated with a case study: the programming of a patient-controlled analgesia pump. In this example, a problem resulting from a generated erroneous human behavior is discovered. The method is further employed to evaluate the effectiveness of different solutions to the discovered problem. The results and future research directions are discussed.

Toward Automated Planning Algorithms Applied to Production and Logistics

In recent years several studies have been made showing artificial intelligence techniques as enhancement proposals for real practical systems. One of such approaches is automated planning, in which knowledge of the system's behavior, expressed through a model, is used by a piece of software denominated automated planner to infer a sequence of actions capable of bringing the system from some initial state to an objective, a so called plan. To do such, the planner relies on some search algorithm capable of exploring the possibilities exposed by the model, and several different approaches have been used by different planners with varying degrees of success. This paper presents an insight on some of the most consolidated ones, both regarding deterministic and probabilistic domains, and focuses on search techniques and generic heuristics in order to assist the development of new algorithms focused on production and logistics. It also covers the main formal system modeling languages, such as STRIPS, PDDL and PPDDL, used by such planners.

R-TNCES: A Novel Formalism for Reconfigurable Discrete Event Control Systems

This study deals with the formal modeling and verification of reconfigurable discrete event control systems (RDECSs). The behavior of an RDECS is represented by that of control components (CCs) and the communication among them. A new formalism, called Reconfigurable Timed Net Condition/Event Systems (TNCES) (R-TNCES), is proposed for the optimal functional and temporal specification of RDECS, which is defined by a behavior module and a control module. The former is a union of various superposed TNCESs, where TNCES-based CC modules are basic units. The latter is a set of reconfiguration functions dealing with the automatic transformations of these TNCESs in response to errors or user requirements by enabling or disabling CC modules, changing condition signals and/or event signals among them, and also treating the state feasibility before and after reconfigurations. To control the verification complexity of R-TNCES, a layer-by-layer verification method is developed, where the similarities of different TNCESs in the behavior module are considered. The contribution of this original paper is applied to a benchmark production system.

Ambitious mitigation scenarios for Germany: A participatory approach

This paper addresses the challenge of engaging civil society stakeholders in the development process of ambitious mitigation scenarios that are based on formal energy system modeling, allowing for the explicit attachment of normative considerations to technology-focused mitigation options. It presents the definition and model results for a set of mitigation scenarios for Germany that achieve 85% CO2 emission reduction in 2050 relative to 1990. During consecutive dialogues, civil society stakeholders from the transport and electricity sector framed the definition of boundary conditions for the energy-economy model REMIND-D and evaluated the scenarios with regard to plausibility and social acceptance implications. Even though the limited scope of this research impedes inferential conclusions on the German energy transition as a whole, it demonstrates that the technological solutions to the mitigation problem proposed by the model give rise to significant societal and political implications that deem at least as challenging as the mere engineering aspects of innovative technologies. These insights underline the importance of comprehending mitigation of energy-related CO2 emissions as a socio-technical transition embedded in a political context.

Generating phenotypical erroneous human behavior to evaluate human–automation interaction using model checking

Breakdowns in complex systems often occur as a result of system elements interacting in unanticipated ways. In systems with human operators, human–automation interaction associated with both normative and erroneous human behavior can contribute to such failures. Model-driven design and analysis techniques provide engineers with formal methods tools and techniques capable of evaluating how human behavior can contribute to system failures. This paper presents a novel method for automatically generating task analytic models encompassing both normative and erroneous human behavior from normative task models. The generated erroneous behavior is capable of replicating Hollnagel's zero-order phenotypes of erroneous action for omissions, jumps, repetitions, and intrusions. Multiple phenotypical acts can occur in sequence, thus allowing for the generation of higher order phenotypes. The task behavior model pattern capable of generating erroneous behavior can be integrated into a formal system model so that system safety properties can be formally verified with a model checker. This allows analysts to prove that a human–automation interactive system (as represented by the model) will or will not satisfy safety properties with both normative and generated erroneous human behavior. We present benchmarks related to the size of the statespace and verification time of models to show how the erroneous human behavior generation process scales. We demonstrate the method with a case study: the operation of a radiation therapy machine. A potential problem resulting from a generated erroneous human action is discovered. A design intervention is presented which prevents this problem from occurring. We discuss how our method could be used to evaluate larger applications and recommend future paths of development.

Anomaly Detection Using Model Generation for Event-Based Systems Without a Preexisting Formal Model

Detecting and debugging faults more efficiently can significantly improve the performance of systems, and a first step toward fault detection is anomaly detection. A new anomaly detection solution is proposed in this paper for event-based systems that consist of processes that interact through shared resources and that do not have a preexisting formal discrete event system model. This solution generates models of the system, assesses the models' performance in detecting faults, and then uses the models and their performance to detect anomalies in new event streams. A new resource-based Petri net formalism is introduced to model these types of systems. The model generation uses an algorithm based on workflow mining to generate resource-based models. The proposed solution is demonstrated on two manufacturing cell examples.